Various methoos have been proposed so that injected fluids can be diverted to uncontacted zones of a reservoir. One such method is disclosed in U.S. Pat. No. 2,402,588 issued to Andresen ("Andresen"). Andresen disclosss a method of sealing a more permeable area of a reservoir by injecting into a reservoir a dilute alkaline solution of sodium silicate uncer low pressure. An acid gas such as carbon dioxide is then injected to reduce the alkalinity of the solution, resulting in gelling.
Another method is disclosed in U.S. Pat. No. 3,645,336 issued to Young et al. ("Young"). Young discloses the plugging of a zone of a reservoir by injecting a mixture of steam and socrum silicate into the permeable zone. A second mixture containing steam and a gelling agent such as carbon dioxide is injected in the permeable zone, ano the two mixtures are allowed to react. A hard silica gel plug is formed.
Yet another method is disclosed in U.S. Pat. No. 3,805,893 to Sarem ("Sarem"). Sarem discloses the formation of a gelatinous precipitate by injection of small slugs of a dilute aqueous alkaline metal silicate solution, followed by water and then a dilute aqueousssolution of a water soluble material which reacts with the alkali metal silicate to form a precipitate. The precipitate hardens to form a substantially impermeable substance.
U.S. Pat. No. 3,965,986 issed to Christopher ("Christopher") discloses still another method. In Christopher, a slug of fumed colloidal silica and water is injected into a reservoir. This slug has a relatively low viscosity. A surfactant is then injected which forms a gel on contact with the silica slug.
Meyers et al. ("Meyers") disclosed a method for reducing the permeability of a subterranean formation in U.S. Pat. No. 4,676,318. Here an alkali metal silicate was produced by injecting into the formation a solution of alkali metal silicate and a chemical surfactant, and a non-condensible gas. The foam hardens into a substantially impermeable solid. The foam may be used to reduce permeabiiity in areas of the formation which have been steam swept during steam stimulation cycles. Thus, subsequent steam stimulation cycles were directed to uncontacted areas of the formation.
In each of the above methods the gas required for forming the foam was injected into the formation. Therefore what is required is a method wnereby a foam can be generated by a gas released in-situ.